The present invention relates to a hydraulically damping elastomer bearing suitable for mountings in a motor vehicle.
German Published Patent Application No. 38 21 240 describes an elastomeric bearing, in which an elastic bearing part, for example, made of an elastic or elastomeric plastic or rubber, is arranged between a sleeve-shaped outer part and an inner part coaxial thereto. With the aid of this bearing part, an elastic connection between the outer sleeve and the inner part is made, which allows relative movements between the parts. The elastomeric bearing also has two chambers which are filled with a liquid damping medium and communicate with one another via a throttle duct. Elastomeric bearings of this type are used in order to mount a vibrating assembly on a non-vibrating holding device. The elastomeric bearings serve, in this context, for vibration insulation or vibration damping. For example, elastomeric bearings of this type are used in vehicle construction in order to mount vehicle axles, a transmission or an engine on the vehicle body. One of the parts is connected to the vibrating assembly, while the other part is coupled to the non-vibrating holding device. The vibrations of the assembly give rise to relative movements between the parts which reduce the volume of one chamber and simultaneously increase the volume of the other chamber. At the same time, the liquid damping medium is exchanged correspondingly between the chambers via the throttle duct. By virtue of the throttling action of the throttle duct, this arrangement results in a damping of the relative movements and therefore to a damping of the vibrations capable of being transmitted between the sleeves.
Due to the selected arrangement of the chambers, conventional elastomeric bearings include a working direction which depends on the application. Thus, a reduction in volume of one chamber, with a simultaneous increase in volume of the other chamber, is possible only for those relative movements between the parts which have a direction component extending parallel to the working direction. Accordingly, a conventional elastomeric bearing can damp hydraulically only those loads or vibrations which include a direction component extending parallel to the working direction. In some applications of such elastomeric bearings, particularly in vehicle construction, however, different loads with different loading directions may occur. For example, on a vehicle, propulsive forces and braking forces, impacts and wheel-load changes in different directions may act on the respective elastomeric bearing.
It is an object of the present invention to provide an elastomeric bearing in which a damping action may be achieved in a plurality of different directions and in which a compact construction is to be ensured for the elastomeric bearing.
The above and other beneficial objects of the present invention are achieved by providing an elastomeric bearing as described herein.
According to one example embodiment of the present invention, an elastomeric bearing includes a plurality of chambers, which are coupled to one another via corresponding throttle ducts so as to ensure two intersecting directions of movement and so that a relative adjustment between the parts reduces the volume in at least one of the chambers and increases the volume in another chamber coupled thereto. Hydraulic vibration damping may thereby be achieved for all the directions of movement which extend in a plane spanned by the intersecting directions of movement or axes.
According to one example embodiment of the present invention, each chamber which is arranged on a first side of the first axis and on a first side of the second axis may communicate, via a first of the throttle ducts, with a second chamber which is arranged on the first side of the first axis and on a second side of the second axis and, via a second of the throttle ducts, with a chamber which is arranged on a second side of the first axis and on the first side of the second axis. It is possible, by virtue of this arrangement of the chambers and throttle ducts, that one of the same chamber may be compressed in the two directions of movement extending parallel to the axes. Furthermore, in such an example embodiment of the present invention, it is possible to equip the first throttle duct and the second throttle duct with different throttling resistances, so that the damping action in the direction of one axis follows a different characteristic curve from that in the direction of the other axis.
In connection with the present invention, the term xe2x80x9con this sidexe2x80x9d describes a position on one side, whereas the term xe2x80x9con that sidexe2x80x9d denotes a position on the other side.
According to another example embodiment of the present invention, one of the axes may extend coaxially to the parts of the elastomeric bearing. Axial loads on the elastomeric bearing are damped correspondingly.
The inner part may include a cover at each of its axial ends, each cover closing two of the chambers axially, and, moreover, each cover including a throttle duct which connects chambers assigned to the cover to one another. By these throttle ducts being integrated into the cover, a compact construction may be obtained for the elastomeric bearing. Moreover, these throttle ducts may be produced relatively simply.
The throttle duct of the cover may be formed by a groove, in the form of an arc of a circle, which is introduced on an axial inner face of the cover. This arrangement generates a streamlined duct shape and may also be implemented at relatively low outlay.
The cover may include, on its inner face, a disc which axially outwardly closes axially a groove in the cover and axially inwardly closes axially the chambers assigned to the cover, the disc including a first orifice, through which the groove communicates with one chamber, and includes a second orifice, through which the groove communicates with the other chamber. A simple construction is obtained, which also makes it possible to produce relatively long flow ducts in the cover. In particular, the throttling action may be set via the length of the flow duct.
The elastomeric bearing has a particularly compact construction when two of the chambers are formed in one axial half of the bearing part and are located diametrically opposite one another with respect to the inner part, while the other two chambers are formed in the other axial half of the bearing part and are located diametrically opposite one another with respect to the inner part. In this example embodiment of the present invention, the first axis of damped relative movements between the parts is oriented coaxially to the parts. The second axis of the relative adjustments, damped by the elastomeric bearing, between the parts is arranged perpendicularly to the first axis.
The inner part may include at least two throttle ducts which extend axially with respect to the inner part and of which one connects to one another the chambers arranged on one side of the inner part and the other connects to one another the chambers arranged on the other side of the inner part. The integration of these throttle ducts into the inner part may result in a compact construction of the elastomeric bearing. Furthermore, the inner part may consist of a considerably more rigid material, for example, metal, than, for example, the bearing part, so that high dimensional stability may be ensured for the throttle ducts accommodated therein.
In order to obtain relatively large duct lengths for the throttle ducts despite the compact form of construction, these throttle ducts are connected to the respectively associated chambers, e.g., in the region of the axial ends of the inner part. For this purpose, for example, the axial end faces of the inner part may have incorporated in them in each case two depressions, via which in each case one of the throttle ducts communicates with one chamber assigned to this end of the inner part. Alternatively or additionally, the inner part may have a cover at each of its axial ends, each cover closing two of the chambers axially, and each cover having, in its axial inner face, in each case two depressions, via which in each case one of the throttle ducts communicates with one chamber assigned to this end of the inner part. By virtue of this construction, these throttle ducts may extend essentially over the entire axial length of the inner part, while the elastomeric bearing has a relatively compact form of construction. The throttling action of the throttle ducts may be influenced over the length of the latter. Furthermore, especially long throttle ducts make it possible, in particular, to accommodate an absorber mass which, for example, is co-adjusted during a flow through the throttle duct, the mass inertia of the absorber mass producing an additional damping action.
The features mentioned above and those described below may be used not only in the combination specified but also in other combinations or alone, without departing from the scope of the present invention.